Temperature responsive electric switch



April 3, 195% F. D. PATTI 2,839,157

TEMPERATURE RESPCNSIVE ELECTRIC SWITCH Filed Aug. 14, 1956 United States Patent TEMPERATURE RESPONSIVE ELECTRIC SWITQH I Fred D. Patti, Morris, Ill.

Application August 14, 1956, Serial No. 603,900

6 Claims. (Cl. 200-438) The present invention relates to a temperature responsive electric switch and more particularly a switch of this type embodying novel means for controlling positive separation of the contacts at temperatures below the selected low temperature limit of the operating temperature range.

It is the general object of the present invention to provide a novel and useful switch of the character indicated which is extremely simple in construction and operation, and may be economically manufactured, while at the same time having great durability and reliability under the most severe operating conditions.

Other and further objects, features and advantages of the present invention will be apparent to one skilled in the art from the following description taken in connection with the accompanying drawing in which:

Fig. 1 is an elevational view of a switch embodying the features of this invention taken from the side of the switch from which the operating shaft projects.

Fig. 2 is a similar view with the operating shaft projecting downwardly and showing the contacts of the switch in on position.

Fig. 3 is a fragmentary view similar to Fig. 2 showing the contacts of the switch in off position in response to deflection of the thermostat blade toward the high temperature end of its operating range as determined by the rotated position of the operating shaft.

Fig. 4 is a similar view showing the switch contacts in open or off position in response to movement or deflection of the thermostat blade at the limit of its movement in a cooling direction beyond the lower temperature end of its operating range. a A temperature responsive electric switch representing a; preferred embodiment of the present invention, as shown in the drawings, includes a resilient switch arm or blade 10, a resilient thermally responsive actuator blade 11 of a bimetallic material having a desired displacement versus temperature characteristic from ambient or room temperature all the way to the high end of the desired operating temperature range, and a button 12 of insulating material carried by an end portion of the blade 11 toward which button the blade is resiliently biased so that the button 12 is capable of engaging the blade 10 at a given position corresponding to normal or room temperature or alternatively engaging said blade to retain the same in a different position between said normal or room temperature position and the high end of its temperature operating range. The blade 10 carries a contact 13 which cooperates with a contact 14 carried by a second resilient switch arm or blade 15 supported intermediate of said contact blade 10 and the actuator blade 11 of bimetallic material. A metal terminal member 16 in conductive engagement with the contact blade 10 and a similar terminal member 17 in conductive engagement with the contact blade 15 provide means for establishing a connection with the electrical circuit to be controlled by the engagement and disengagement of the cooperating contacts 13 and 14. Each terminal member 16 and 17 and the contact blades 10 and 15 respectively associated therewith have eyelet-shaped ends which are disposed around a tubular supporting fastener or post 18. One end of the post 18 is staked or otherwise suitably fastened through an opening in a rigid bracket 19 as at 20. The opposite end of the post 18 is provided with an enlarged head 20 and a series of insulating spacers or bushings 21, 22 and 23 fitted about the post 18 and with which the blades 10, 15 and 11 and members 16 and 17 are interleaved as shown in the drawings, cooperate to secure the blades 10, 15 and 11, the members 16 and 17 and the bracket 19 in stacked, insulated relation with the contacts 13 and 14 in aligned relation along an axis in spaced parallel relation to the post 18.

The second contact blade 15 is resiliently biased toward the blade 10 and against an insulating tip or stop 24. The stop 24 extends through an opening in the blade 10 and forms the forward or inner extension of an operating shaft 25 which has threaded engagement with an internally threaded nut 26 fixed to the bracket 19 in coaxial alignment with and surrounding an opening in the bracket 19 at a distance away from the post 18. The nut 26 has a threaded external surface engageable by an outer mounting nut 26 and an inner mounting nut 26* whereby the switch may be supported on a panel or other suitable supporting member by tightening the outer nut 26 against the outer surface of such a panel while the surface of the inner nut 26 facing the nut 26 engages the inner surface of the panel. Thus the bracket 19 may be mounted on a fixed panel or support by means of a suitable fastener having entry through the tubular post 18 or by means of the shaft 25 in cooperation with themounting nuts 26 and 26 By means of a knob or other suitable finger engaging handle (not shown) fitted on the outer end of the shaft 25 opposite the end carrying the tip or stop 24, the shaft 25 may be rotated and because of the threaded interengagement of the shaft 25 and the nut 26, and through such rotation of the shaft 25 the stop will be moved axially whereby the limit position of the second contact blade 15 and its associated contact 14 may be adjusted as desired. A dog 27 forming an axial extension of the end of the shaft 25 facing the contact blade it has engagement with a tongue 29 forming a reduced extension of a leaf spring 3% secured about the post 13 between the bracket 19 and the surface of the insulating spacer facing said bracket 19,- to limit the rotation of the shaft 25 to an arc of desired distance less than one complete revolution. Thus in one limit of rotation of the shaft 25, as shown in Fig. 4, the contacts 13 and 14 of the blades 151 and 15 are in off position in response to the stop 24 being located in its most advanced position relative to the plate 19.

In a less advanced position of the stop 24 as shown in Fig. 2 and Fig. 3, the blade 15 is allowed to occupy an inclined position toward the bracket 19 with the result that the contacts 13 and 14 are in engaged or on position as in Fig. 2 and the bimetallic blade 11 has not yet assumed a position of deflection sufiicient to move the blade 1% in the direction of the bracket 19. At the high operating temperature of the range determined by the position of the stop 24, as in Fig. 3, the bimetallic blade 11 has undergone sufiicient deflection to move the blade 1% a distance wherein the contacts 13 and 14 are in disengaged or off position.

The tongue 29 of the leaf spring 341 applies suflicient friction against the annular end surface of the shaft 25 engaged by the tongue 29 to yieldably hold the shaft 25 against accidental or unintentional rotation from a selected adjusted position of the dog 27 relative to said tongue 29. An car 28 sheared and bent out of the plane of the springfitl interengaged with an opening in the bracket 19 aligned therewith provides means for locking the spring 30 against displacement about the post 18 as an axis.

Reference numeral 31 desginates a second resilient thermally responsive actuator blade of bimetallic material having an eyelet shaped end portion fitting about the post 18 and held in stacked relation to the actuator blade 11 between a conductive spacer 32 engaging the clamped face of the blade ll facing the head 20 and surface of the head 29' facing the blade ill. The blade 31 is arranged to present its metal layer of greatest thermal expansion in facing relation to the blade 11 with the result that the blade 31 will bedefiected away from the blade ll under the influence of increasing temperature, as in the position of the parts shown in Fig. 3 wherein the blade 11 is operative to move the contact blade it) a sufficient distance away from the contact blade 15 to place the contacts 13 and 14 in off position. As the temperature decreases and approaches a normal or room temperature, the blades 11 and 31 will assume a parallel position as shown in Fig. 2 and finally upon further cooling of the blades 11 and 31, they will move into interengaged position as shown in Fig. 4 wherein the blade 1 is effective to limit further deflection of the blade 11 in a cooling direction. it will thus be seen that by using blades 11 and 31 of bimetallic material having substantially equal displacement versus temperature characteristics, such interengagement will take place on a line parallel to and midway of the space between tie blades 11 and 31 when the blades 11 and 31 are in such spaced apart relation as shown in Fig. 2. It will also be observed that such positive control of the deflection of the blade 11 in a cooling direction positions the contacts 13 and 14 relatively close to the position of the contacts when the latter are at a station corresponding to the lower end of the operating temperature range.

In accordance with the present invention as described and illustrated herein, provision is made for a temperature responsive electric switch construction and design having a positive off position and minimum amount of lost motion in the adjusting mechanism thereof between its oil position and the low end of its desired operating range of adjustment.

It will also be understood that minor variations and changes in the exact details of construction will be ap parent to persons skilled in the art of thermal switches and accordingly it is intended that this invention shall cover all such changes and modifications as fall within the scope of the claims appended hereto.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A temperature responsive electric switch assembly having two relatively movable switch blades, cooperating said switch blades to engage and disengage the contacts in response to predetermined variations from a selected operating temperature, a rigid support on which said switch blades and said thermally responsive blade are fastened in stacked relation with said thermally responsive blade and the switch blade controlled thereby in straddling relation to the other switch blade, and means obstructing movement of said thermally responsive blade in a direction away from the switch blade controlled thereby under predetermined temperature conditions including a second resilient thermally responsive blade secured to said support in opposed relation to the surface of said first thermally responsive blade which faces away from the area occupied by said switch blades.

2. A switch assembly as defined in claim 1 wherein the thermally responsive blades are in clamped stacked relation at one end thereof, and a spacer separates said thermally responsive blades at said clamped end of the blades.

3. A switch assembly as defined in claim 1 wherein each thermally responsive blade has a displace'mflnt versus temperature characteristic similar to that of the other thermally responsive blade.

4. A switch assembly as defined inclaim 1 wherein an insulating member carried by said first thermally responsive blade is operable to move the switch blade controlled by said first thermally responsive blade in a direction away from the other switch blade,

5. A switch assembly as defined in claim 1 wherein the switch blade straddled by the first thermally responsive blade and the switch blade controlled by said first thermally responsive blade is resiliently biased into engaged position with an insulating member forming an extension ofa threaded operating shaft rotatably mounted about a fixed axis in relation to said support.

6. A switch assembly as defined in claim 5 wherein rotation of the shaft is controlled by a leaf spring secured about said rigid fastening member between the bracket and the switch blade nearest said bracket, and means for locking the spring against displacement about said fastening member as an axis includes an car on said spring interengaged with an opening in said bracket.

References Cited in the file of this patent UNITED STATES PATENTS 

